It is well known that patients who are confined to a bed or chair for extended periods of time are at risk of developing pressure ulcers, i.e., decubitus ulcers, pressure sores, or bed sores as they are more commonly known. These ulcers are often seen to develop within soft tissue that is compressed between a bed or chair surface and a patient's weight-bearing bony prominences, the compressed tissue being at least partially deprived of oxygenated blood flow. A continued lack of blood flow, and resultant lack of oxygen, can result in cell death which may be evidenced in the form of pressure sores. Pressure sores do not become apparent immediately, but rather form over time, with the development speed depending on a number of factors including the firmness and friction of the supporting surface against the patient's skin, the tissue temperature at the site of the ischemic condition, the amount of moisture in contact with the skin, and the health and susceptibility of the skin to such injury due to age or illness.
One venerable and generally accepted means of reducing the risk of decubitus ulcer development in immobile patients is to move or turn them regularly to a position where the previously compressed tissue is no longer weight bearing, usually at approximately two-hour intervals. For example, a patient in a back rest position might be periodically rolled to one side or the other, such motion helping to maintain blood flow to soft tissue that is under compression. Similar strategies are employed for patients that are confined to a chair for long periods of time. Obviously, an assisted-movement strategy relies to a large extent on the vigilance of the (often harried) attending staff to insure that the patient is properly relocated. Further, it is far too easy for the busy caregiver to let the time for turning the patient slip by in the press of other daily emergencies. To the extent that the caregiver is too busy or forgets to perform this service in a timely manner, this method can fail to achieve its intended purpose. Further, this sort of strategy can be counterproductive for use with the patient who has some capacity for self movement as, for example, where at the next scheduled turn a patient is moved by the nurse back into a position from which he or she had just moved scant minutes before.
More particularly, the process of moving a patient to another position is admittedly disruptive to the patient and this is especially true at night, since the patient—if he or she were sleeping—will be awakened for the purpose of relocation. The typical two-hour movement interval must be observed around the clock if the method is to be effective, so it is necessary to rouse the patient—who might be sleeping soundly at the time—to make the required adjustment in position. Further, this adjustment might not have even been necessary if the patient had recently moved of his or her own volition. Thus, in many situations it would be advantageous for the caregiver to know if and when the patient last moved him or herself. Then, if the last movement were within a prescribed period of time, it might be possible to spare the patient an unnecessary interruption in his or her healing sleep. The caregiver would then relocate the sleeping patient, only if that relocation were actually required. Further, knowing which patients do not need to be moved could result in a substantial savings in labor costs, as the time that would otherwise be devoted to moving the patient that did not actually need to be moved could be productively applied elsewhere. That being said, as useful as this sort of information might be to the health care provider, however, the present state-of-the-art in patient management does not provide this sort of information.
Generally speaking, there are two broad prior art approaches to dealing with decubitus ulcers: mechanical and medicinal. The mechanical approach is aimed at reducing the severity of bedsores through the use of a specialized mattress, pad, or other arrangement, which is designed to lessen the weight-pressure that is brought to bear on the patient's bony prominences. These devices might be either static (e.g., foam, air, or water mattresses) or dynamic (e.g., compartmentally inflatable mattresses that dynamically shift the locus of support pressure under the patient in response to the patient's movements). Examples of inventions in the prior art that are generally concerned with this subject matter are U.S. Pat. No. 4,425,676, 5,926,884, and 5,072,468, the disclosures of which are incorporated herein by reference.
On the other hand, the medical—or second inventive—approach is concerned with the development of medicinal compounds and methods of treating the ulcer after it occurs. This approach is obviously useful but reactive, rather than proactive, as it attempts to minimize the damage occasioned by the ulcer after it has formed.
However, neither of the above approaches is directed toward the prevention of pressure sores which would, of course, be preferably for proper patient care.
General information relating to mats for use in patient monitoring may be found in patent application Ser. No. 09/285,956 filed Apr. 2, 1999, now U.S. Pat. No. 6,307,476, the disclosure of which is specifically incorporated herein by reference. Additionally, U.S. Pat. Nos. 4,179,692, 4,295,133, 4,700,180, 5,600,108, 5,633,627, 5,640,145, and 5,654,694 (concerning electronic monitors generally) contain further information generally pertinent to this same subject matter, as do U.S. Pat. Nos. 4,484,043, 4,565,910, 5,554,835, and 5,623,760 (switch patents), and U.S. Pat. No. 6,646,556 and patent application No. 60/487,021 (mats for use in preventing decubitus ulcers) the disclosures of all of which are all incorporated herein by reference.
Heretofore in the patient monitoring arts there has been no apparatus or method aimed specifically at reducing the risk of bedsores in a semi-invalid patient, i.e., the patient who at least occasionally moves without assistance. With a semi-invalid patient, assisted repositioning—whether manual or mechanical—should only take place if the patient has not moved for some particular period of time. This, of course, suggests the need for a method and apparatus for monitoring the patient so that the time when he or she last moved can be determined. Further, the duration of the patient's move should also be monitored to ensure that tissue reoxygenation takes place. Finally, there is a need for an apparatus that can monitor, record, and report the overall amount of patient self-induced and/or caregiver assisted movement, so as to give the caregiver (or that person's supervisor) some estimate of the amount of movement by the patient in the bed with respect to time. Those of ordinary skill in the art will recognize that historical estimates of the overall amount of patient movement are directly useful to the staff and further useful in generating, for example, decubitus ulcer patient risk indices such as the Braden or Norton scale.
Heretofore, as is well known in the patient monitor arts, there has been a need for an invention to address and solve the above-described problems. Accordingly, it should now be recognized, as was recognized by the present inventors, that there exists, and has existed for some time, a very real need for a system for monitoring patients that would address and solve the above-described problems.
Before proceeding to a description of the present invention, however, it should be noted and remembered that the description of the invention which follows, together with the accompanying drawings, should not be construed as limiting the invention to the examples (or preferred embodiments) shown and described. This is so because those skilled in the art to which the invention pertains will be able to devise other forms of this invention within the ambit of the appended claims.